They have also set up a special award in her honour after she failed to qualify for the adult-only competition.
Katie Davies, a pupil of Swansea's Birchgrove comprehensive, was entered for the Leading Wales Awards by her headteacher Julian Doroszczuk.
But the 16-year-old, who is in charge of the Rainbows at Birchgrove, Swansea, was facing disappointment because she was not old enough. Judges, however, were so impressed with her that they invented a new 14-25 category. They also set up a meeting with former Boom Town Rat Sir Bob in Cardiff.
Katie is passionate about raising money to help beat world poverty and she is a big fan of the pop singer who organised the Live Aid concerts.
Barbara Chidgey, Leading Wales Awards chairperson, said: "We approached Business to Business who had invited Sir Bob Geldof to Cardiff," she said.
"He was on a very tight schedule, but we managed to set it up."
Delighted Katie said: "He told me to do whatever I thought was right and to have no regrets. I found him totally inspirational."
She had her picture taken with him and said it was one of her most treasured possessions.
Mrs Chidgey said: "We were very impressed by what Katie has managed to do.
She is an excellent role model - a very calm and determined person who has a big impact."
Head girl Katie, a girl guide, said: "I had the choice of either going on to become a ranger or working with the little ones, and I opted for that."
She will now head a 15-strong pack of brownies aged five up to seven, as well as being involved in charity work with her school.
Fundraising causes at her school include the shoebox appeal organised by the Salvation Army, Comic Relief, Children in Need and Macmillan Nurses.
Katie has organised coffee mornings and sold wristbands to raise money.
Judges for the Leading Wales Awards are currently inviting nominations for people demonstrating good leadership in the public sector, private enterprise and voluntary organisations.
Nominations close on November 24 and can be made online at www.leadingwalesawards.com or by ringing 02920 496464